The goal of this project is to develop and adapt Electron Spin Resonance Spectroscopy to study the biochemistry, physiology, and pathology of cells and tissues in order to answer problems of medical and biological importance. To accomplish this goal we are working on approaches to increase the sensitivity and developing cavity design suitable for different problems ranging from microsamples, to cultured cells to whole tissues. Over the past year an X-band spectrometer has been assembled. A technique was developed for calculating intramolecular distances using Electron Spin Resonance, and it was applied to measure the distance between the 2 metal binding sites of the iron carrier protein transferrin a critical question in the field of iron metabolism. This technique is currently being applied to determine the location of receptor proteins on the cell plasma membrane or within the cell cytoplasm. Electron spin resonance has a major advantage over the conventional morphologic and cell fractionation techniques in that the integrity of the cell is maintained. The important anticancer drug adriamycin was also studied to determine how it kills tumor cells and how it induces a cardiomyopathy, which is the third most common cardiomyopathy in the United States. It was demonstrated that (Fe(III) binds to adriamycin and that these complexes then cycle to reduce oxygen. The Fe(III) bound to adriamycin is reduced to Fe(II) which then donates an electron to oxygen, regenerating Fe(III) - adriamycin. Numerous studies have shown that the therapeutic and toxic effects of adriamycin are due to the formation of reactive oxygen radicals and this mechanism provides an explanation of how these radicals are formed.